Maximum available manifold pressure and brake horsepower computer



May 15, 1951 K. H. CHAPPLE ET AL 2,553,526

MAXIMUM AVAILABLE MANIFOLD PRESSURE AND BRAKE HORSEPOWER COMPUTER Filed Sept. 12, 1947 s Sheets-Sheet 1 KENN ETH H. OHAPPLE RAYMOND E. KITTREDGE INVENTORS W ATTORNEY May 15, 1951 K. H. CHAPPLE ET AL MAXIMUM AVAILABLE MANIFOLD PRESSURE AND BRAKE HORSEPOWER COMPUTER 8 Sheets-Sheet 2 Filed Sept. 12, 1947 FIG. 2

KENNETHHCHAPPLE RAYMOND EKITTREDGE INVENTOR BY y ATTORNEY FIG. IA

May 15,1951 K. H. CHAPPLE ET AL MAXIMUM AVAILABLE MANIFOLD PRESSURE AND BRAKE HORSEPOWER COMPUTER 8 Sheets-Sheet 3 Filed Sept. 12, 1947 KENNETH H.0HAPPLE RAYMOND E. KITTREDGE INVENTOR ATTO R N EY ALTITUDE y 1951 K. H. CHAPPLE ET AL 2,553,526

MAXIMUM AVAILABLE MANIFOLD PRESSURE AND BRAKE HORSEPOWER COMPUTER Filed Sept. 12, 1947 8 Sheets-Sheet 5 MAX I MUM AVAILABLE MANIFOLD PRESSURE (HIGH BLOWER) FIG.6

MAXIMUM AVAILABLE MANIFOUD PRESSURE (LOW BLOWER) 4O MANIFOLD PRESSURE FIG. 8

KENNETH H. GHAPP'LE RAYMOND E. KITTREDGE 3O JNVENTORS BY WXV/W MANIFOLD PRESSURE ATTORNEY ALTITUDE K. H. CHAPPLE ET AL 2,553,526 MAXIMUM AVAILABLE MANIFOLD PRESSURE AND BRAKE HORSEPOWER COMPUTER 8 Sheets-Sheet 6 .a on o .w 7 5 o 6 2 m 8 6 o M w 0 0 w 3 W M. w .r M 5 2 O 5 6 4 o 2 s .w ,54 nmmmmcmm .m 2 77 m 6 2 4 HQ 0 m 0 0 w :w 0 o 6 T M 3 1/4 6 o 0 2 F 0 3 O m 0 0 O a m l 5 e AW 0 4 0 a m 87 0 2 2 9 N 2 3 4. 3 0 6v 2 0 4 3 6 o 6 o 2 6 8 a B u o V 2 0 A 00 4 V w 5 0 6 2 2 z 3 4 3 u m 3 3 m e a 3 O I NPOO 4 2 .l B 8 O 4 M 3 4 W MMQ 2 3 N 8 2 3 7 a 4 4 e w 0 4 G 6 a 6 I 3 w V F 3 a v 2 w o 3 3 4 3 B 3 O 4 2 4 M May 15, 1951 Filed Sept. 12, 1947 KENNETH .CHAPPLE RAYMOND E.K|TTREDGE JNVENTORS BY ATTORNEY INVENTORS ATTORNEY KENNETH H. OHAPPLE RAYMOND E. KITTREDGE 8 Sheets-Sheet 7 4 m O O H w 0 M M M w 5 4 4 0 w 4 wm DJ 5 4 5 3 W19 01:2 E 2 6 8 K. H. CHAPPLE ET AL MAXIMUM AVAILABLE MANIFOLD PRESSURE AND BRAKE HORSEPOWER COMPUTER mlzma J, 4 o 2 o May 15, 1951 Filed Sept. 12, 1947 8 Sheets-Sheet 8 KENNETH H GHAPPLE RAYMOND E. KITTREDGE INVENTORS ATTORNEY CHAPPLE ET AL W/z M K. H. MAXIMUM AVAILABLE MANIFOLD PRESSURE AND May 15, 1951 BRAKE HORSEPOWER COMPUTER Filed Sept. 12, 1947 Nmm WWW oz 9% mom PF vmm w .omm\ o .I mmm 3m 3., m z wmm cow 2% wow wow 3 N8 m mow 0 6 F 2 m F $5 9}, mm? N 8% www mwm I m 3w o5 3m 9% im mom 3m 0% 0mm mom 2 7 $3031 1 125 52 4 I: o h m r I l I I I llvl llllllllll IIL F iatented 15, 195i MAXIMUM AVAILABLE MANIFOLI) PRES- SURE AND BRAKE HORSEPOWER COM- PUTER Kenneth H. Chapple, Binghamton, and Raymond E. Kittredge, Port Dickinson, N. Y., assignors to Link Aviation, Inc., Binghamton, N. Y., a corporation of New York Application September 12, 1947, Serial No. 773,662

7 Claims. 1

This invention relates to the art of grounded aviation trainers, and more particularly to an engine simulator forming a part of such trainers.

Grounded aviation trainers of the type to which this invention relates are generally mounted upon a stationary base and include a fuselage having a seat for a student and an instrument panel positioned ahead of the seat. The instrument panel carries a complement of instruments which simulate the instruments carried by the plane whose performance is being simulated by the trainer. Positioned within the fuselage are manually operable controls, such as the throttle lever, engine speed control lever, supercharger control, rudder pedals and stick or column control, which controls simulate the corresponding controls of the real plane represented by the trainer. Suitable computing devices are interposed between the manual controls in the cockpit and the instruments on the instrument panel to cause the instruments to give the same indications as the instruments in a real plane would give in the presence of corresponding actual control settings.

The invention of this application relates to improved computers interposed between the manual controls in the fuselage and the instruments on the instrument panel to cause the instruments to properly register according to the positions of the manual controls.

The engine of the type being simulated by the apparatus of this application is equipped with a manifold pressure regulator which automatically controls the butterfly valve associated with the engine to maintain the manifold pressure of the engine at the value for which the throttle lever (sometimes referred to in the case of engines equipped with such a regulator as the boost control) is set at all timesas long as the combined factors of altitude and engine speed are such that a manifold pressure equal to or greater than the manifold pressure for which the throttle lever is set can be obtained with the butterfly valve wide open. If the combined factors of engine speed and altitude are such that a manifold pressure equal to the manifold pressure for which the throttle lever is set cannot be obtained, it follows that the manifold pressure regulator cannot maintain the manifold pressure for which the throttle lever is set.

Accordingly, in the case of an engine of the type being simulated, for any combination of engine speed and altitude there is a maximum manifold pressure which may be obtained. If the throttle lever is set to produce a given manifold pressure, the manifold pressure regulator will automatically maintain the manifold pressure at that level regardless of changes in altitude and engine speed until the increase in altitude or decrease in engine speed, or both, are

such that the manifold pressure cannot be produced, regardless of throttle setting. Thereafter, an increase in altitude or decrease in engine speed progressively decrease the manifold pressure which may be produced.

The functioning of an engine equipped with a manifold pressure regulator is simulated by the apparatus of this invention in the following manner:

The simulated throttle lever in the trainer is connected through intermediate mechanism to the simulated manifold pressure indicator, so that the reading of the indicator is normally controlled solely by the setting of the lever. Consequently, the student can set the lever to cause the indicator to give the desired simulated manifold pressure indication, just as in the case of the pilot flying a real plane the pilot sets the throttle lever to produce the desired manifold pressure.

In order to simulate the limiting effect of altitude and engine speed upon manifold pressure, there are provided by the apparatus of this invention a pair of maximum available manifold pressure computers which continuously compute the maximum available manifold pressure for the prevailing assumed engine speed and assumed altitude. The output of one of the maximum available manifold pressure computers at all times limits the reading of the simulated manifold pressure indicator so that the indicator cannot indicate a higher assumed manifold pressure than the prevailing assumed engine speed and assumed altitude should permit, regardless of the fact that the simulated throttle lever may be set to produce a higher simulated manifold pressure.

Two maximum available manifold pressure computers are provided because the engine of the type being simulated is provided with a supercharger control by means of which the pilot can cause the supercharger to run on the high blower" or low blower. The maximum available manifold pressure in the case of the engine being simulated, for any given assumed engine speed and any given assumed altitude, varies depending upon whether the supercharger is running on high blower or low blower. Accordingly, the apparatus of this invention provides a manual control which simulates the supercharger control of a real plane, and when this control is in the assumed high blower position one of the maximum available manifold pressure computers limits the reading of the manifold pressure indicator according to assumed engine speed and altitude, and when the control is in the assumed low blower position the other computer limits the reading of the indicator according to assumed engine speed and altitude.

Another important feature of the invention is a novel brake horsepower computer which combines the factors of assumed manifold pressure and assumed engine speed to determine the assumed sea level brake horsepower. The output of the brake horsepower computer is then modified by the factor of assumed altitude to produce the factor of brake horsepower at altitude.

The maximum available manifold pressure computers and the brake horsepower computer of this application are of the general type disclosed in the co-pending application of H. Frederick schaefer, Jr., Serial Number 737,696, filed March 27, 1947 for Computer for Aviation Trainer and the Like.

The engine being simulated is equipped with a constant speed propeller, and another portion of the apparatus of this invention limits the assumed engine speed, as indicated by the provided simulated tachometer, when the throttle simulating lever is positioned rearwardly of the point required to produce the necessary assumed manifold pressure to maintain the assumed engine speed for which the provided simulated engine speed control lever is set.

Other associated features of the apparatus of this invention will become apparent upon a reading of this description.

For a detailed disclosure of the apparatus of this invention reference is made to the accompanying drawings wherein,

Fig. 1 shows the simulated throttle control and engine speed control levers, as well as the maximum available manifold pressure computers, while Fig. 1A discloses the throttle lever compensating spring arrangement.

Fig. 2 discloses the brake horsepower computer and associated apparatus.

Fig. 3 shows the manifold pressure transmitter and associated apparatus.

Fig. 4 is a rectilinear graph showing the brake horsepower produced by the engine being simulated for various manifold pressures and engine speeds, while Fig. 5 shows the data given by the graph of Fig. 4 replotted in curvilinear form as well as the schematic construction of the brak horsepower computer.

Fig. 6 is a rectilinear graph showing the manifold pressures produced by the engine being simulated for various engine speeds and altitudes when the supercharger is operating on high blower, while Fig. 7 shows the data given by the graph of Fig. 6 replotted in curvilinear form as well as the schematic construction of the maximum available manifold pressure computer for the high blower supercharger condition.

Fig. 8 is a rectilinear graph showing the manifold pressures produced by the engine being simulated for various engine speeds and altitudes when the supercharger is operating on low blower, while Fig. 9 shows the data given by the raph of Fig. 8 replotted in curvilinear form as well as the schematic construction of the maximum available manifold pressure computer for the low blower supercharger condition.

Fig. 10 is a detailed view of a portion of the maximum available manifold pressure computer for the low blower supercharger condition which is shown generally in Fig. 1.

Fig. 11 is a schematic diagram of the electrical circuits associated with the apparatus of this invention shown in the other drawings.

Fig. 12 shows the relative positions in which Figs. 1, 2 and 3 may be placed to present a single View of the apparatus of those figures.

Fig. 13 discloses a portion of the electrical apparatus associated with the apparatus of Fig. 1.

Reference is made to Fig. l where the lever l8 which simulates the throttle control lever of a real plane is shown, this lever being movably mounted upon the rod l2 which is fixed within the fuselage of the trainer in a position corresponding to the positioning of the throttle control lever of a real plane. The trainer fuselage is not disclosed herein. The rear end of link 14 is pivotally attached to the lower end of lever I0, and mounted upon the forward end of link I4 is a positive type centering arrangement designated generally by iii. A detailed disclosure of this arrangement is shown in Fig. 1A wherein it is seen that there is affixed upon the link 14 the sleev H] which moves at all times with the link H}. An outer sleeve 20 encases the inner sleeve I8, and a pair of washers 22 and 2E encircle link I4, one of these washers bearing against each end of the two mentioned sleeves. A rear spring 26 encircles link I4, the forward end of this spring bearing against the washer 24, and the rear end of this spring bearing against the washer 28. The cotter pin 30 prevents washer 28 from moving to the rear under the compression of spring 25. A forward spring 32 is provided, the rear end of this spring bearing against the washer 22, and the forward end bearing against the washer 34 which is prevented from moving forward along link l4 by the cotter pin 36.

To the outer sleeve 29 is affixed the pin 38, upon which is mounted the upper arm of bellcrank 40, this bell crank being pivoted upon the rod 42 which also is suitably fixed within the fuselage of the trainer. The upper end of link 44 is pivotally attached to the lower arm of bellcrank 40, and the lower end of the vertical link 44 is pivotally attached to the lower arm of bellcrank 45. The bellcrank 46 is pivoted upon the fixed rod 48 which is suitably fixed inside the fuselage of the trainer. The forward end of link 50 is pivotally attached to the upper arm of bellcrank 46, and afiixed upon the rear end of link 50 is the washer 52 against which normally bears the rear end of sleeve 54 which is free to slide upon link 55 The rear end of spring 56 bears against the forward end of sleeve 54, while the forward end of this spring bears against the washer 58 which is affixed upon link 50.

' A pin 60 is attached to sleeve 54 and to the upper end of lever ,62 which is freely mounted upon the horizontal shaft 64 which is suitably rotatably mounted in brackets which are affixed within the trainer fuselage. One such bracket, 66, is shown in Fig. l, but the other supporting brackets are not shown.

Pivotally attached to the lower end of lever 62 is the forward end of link 68, the intermediate portion of which is shown in Fig. 2 and the rear portion of which is shown in Fig. 3. In the latter figure it will be seen that the rear end of link 88 is pivotally attached to the lower arm of bellcrank 10. which bellcrank is aflixed upon the horizontal shaft 7.2 by means of set screw M. The forward arm of bellcrank lll has pivotally attached thereto thelower end of link 16, the upper end of which is pivotally attached to the forward end of arm 18, the rear end of which is affixedv upon the horizontal shaft by means of set screw 82. Upon the right end of shaft 89 is affixed the gear 84 which drives the gear 86 to which is affixed the arm 88. Gear 86 and arm 83 are free to rotate upon the shaft 90. The rear end of link 92 is pivotally attached to the outer end of arm 88, the forward end of link 92 being shown in Fig. 2 to be pivotally attached to the lower end of arm 94 which together with the arm 234 forms the bellcrank 98. This bellcrank is pivotally mounted upon the stud I which is carried by the fixed bracket I02, suitable spacers I04 being provided to offset the bellcrank 98 from the bracket m2. Bracket I02 is suitably fixed to the inside of the trainer fuselage.

Returning now to Fig. 3, the shaft 72 serves as the input shaft of the reversible follow-up motor or power amplifying assembly which is shown in block form and designated I I2. Inasmuch as the construction of the assembly I I2 is well known by those skilled in the art, a detailed disclosure of the same is not deemed necessary. This assembly may, for example, be of the type disclosed in Fig. 5A of U. S. Patent 2,439,169 dated April 6, 1948 and maturing from an application filed in the name of Raymond E. Kittredge. The assembly I I2 has a first output in the form of the previously mentioned shaft 90 which forms the input of the potentiometer II4 which may be connected by the electrical conductor Hi; to the other parts of a noise generating system II? for producing sound effects simulating the running of the engine of a real aircraft. Potentiometer H4 is the volume control for such a system, and for a detailed disclosure of such a system reference is made to the copending patent application of Stanley I. Hayes and Milton S. Wade for Grounded Pilot Training Apparatus, Serial Number 634,492 filed December 12, 19 :5, now Patent Number 2,510,500, issued June 6, 1950.

A second output of the assembly I I 2 is the shaft H8 which is the input of the Selsyn-type transmitter I20 which is connected by conductor I22 to Selsyn receiver I24d which forms a part of an indicator designated generally by I25; and which simulates the manifold pressure indicator of a real plane, this indicator including a dial IZ la which is graduated like the manifold pressure gauge of a real plane and a pointer 22% afiixed upon the shaft I240 which is the output shaft of the Selsyn type receiver I24d.

In view of the above described arrangement, it will be appreciated that when the lever I0 simulating the throttle control lever of a real plane is moved ahead in Fig. 1, in simulation of theopening of the throttle in a real plane, the link I4 moves to the rear and by means of the spring as,- sernbly I6 and bellcrank 40 this motion is transferred to link 44 which moves upwardly. The motion of link 54 is transferred to link Ed by bellcrank 35, resulting in a movement to the rear of link 56 By means of washer 50, spring 55, sleeve 54 and pin 50, lever 52 is rotated clockwise, and link 68 moves ahead, resulting in a clockwise rotation of the bellcrank TEE in Fig. 3 and in an upward movement of link IS in the same figure.

Arm I8 is rotated clockwise as is shaft 85! and gear 84, while gear 86 and arm 88 are rotated in the opposite direction, resulting in a movement to the rear of link 92 and in a counterclockwise rotation of the bellcrank 08 in Fig. 2.

When the bellcrank 10 in Fig. 3 is rotated clockwise, the shaft I2 moves in the same direction, resulting in an energization of the power amplifying assembly II2. The rotation of the output shaft 90 operates the volume control II4 to cause the noise producing system to generate a louder noise. The rotation of the shaft H8 operates the Selsyn transmitter I29 to cause the manifold pressure indicator I24 to indicate a higher assumed manifold pressure.

Without a detailed explanation, it will be appreciated that when the lever I0 in Fig. 1 is moved to the rear in simulation of the closing of the throttle of a real plane, all of the previously described apparatus will move in the opposite directions from those just described, resulting in a lower indicated assumed manifold pressure, a lower intensity of engine simulation noise, and a clockwise rotation of the bellcrank 98 of Fig. 2. Accordingly, the simulated manifold pressure indicator I24 is normally operated by the simulated throttle lever II] to give an indicated assumed manifold pressure dependent only upon the setting of the lever. This arrangement simulates the operation of an engine equipped with a manifold pressure regulator wherein the regulator maintains the manifold pressure at the level for which the throttle lever is set, providing the engine speed and altitude are such as to permit the same.

Reference is again made to Fig. 1 where the lever I30 is shown, this lever simulating the engin speed control lever of a real plane. This lever is pivotally mounted upon the previously mentioned rod I2, and the rear end of link I32 is: pivotally attached to the lower end of lever I30. The forward end of link I32 is pivotally attached to the upper arm of bellcrank I34 which is pivoted upon the previously mentioned rod 42, the upper end of link I35 being pivotally attached to the lower arm of bellcrank I34. The upper arm of bellcrank I38 is pivotally attached to the lower end of link its, this bellcrank being pivoted upon the fixed rod I52, and the forward end of link I42 is pivotally attached to the lower arm of bell- I crank I38. The rear end of link I42 is shown in Fig. 2 as having its rear end pivotally attached to the lower end of lever I44 which is freely mounted upon the shaft I45 which forms the input shaft of the R. P. M. transmitter I48 which is shown in block form. This transmitter may take the form of a conventional reversible follow-up motor similar to the assembly I I2 shown in Fig. 3, and being well known to the art, is not shown herein in detail.

Integral with the lower portion of lever I44 is the forwardly extending extension I44a, to which is pivotally connected the rear end of link I59, the forward end of which is shown in Fig. 1 as being connected to the extension I54 of arm I 56, the lower end of which is pivoted upon stud I58 carried by the fixed bracket Eli.

Returning to Fig. 2, the upper end of lever I46 carries the pin 0 to which is attached the upper end of spring I62, the lower end of which is attached to the stud I64 carried by the arm lei-5 integral with hub I50 which is affixed upon the input shaft I46 of the R. P. transmitter I48 by means of set screw I30. Also integral with hub IE8 is the downwardly extending arm I72. The arm I55, hub I63 and arm I72 form a bellcrank numbered H4.

The lower end of lever I44 carries a pin I15 projecting from the right side thereof, which pin is arranged to engage the forward edge of the arm I??? under conditions to be described.

The arm I12 carries the pin III which is swiveled within block 519. This block in turn has swiveled therewithin the vertical pin I18 which is affixed to the slider I which encircles the forward end of link I82, and a collar I84 is aflixed upon the forward end of link I82.

The previously mentioned link I82 extends to the rear in Fig. 2, and in Fig. 3 it will be seen that the rear end of this link is pivotally attached to the outer end of arm I86 which is integral with 7 hub I88 which is freely mounted upon the shaft III). A second hub I80 is fixed upon the shaft IIS by set screw l9! and has integral therewith the arm I92. A pin I84 carried by the outer end of arm I8 3 projects from the left side of arm 185 to be engaged by the upper edge of arm I92 under conditions to be described.

The R. P. M. transmitter I48 of Fig. 2 has two output shafts, I98 and 28 .9. The shaft I98 forms the rotor of potentiometer 282 which is connected by conductor 2% to the voltmeter type instrument 281 which simulates the tachometer of a real plane, and which includes a dial 261a graduated like the tachometer dial in a real plane and a needle 2811) arranged to move over the dial to indicate the assumed engine speed. The shaft 296 is the R. P. M. input to the brake horsepower computer shown in Fig. 2 and designated generally by 288.

Considering now the functioning of the apparatus just described, when the R. P. M. lever I38 of Fig. 1 is moved ahead to produce a higher assumed engine speed, the link I32 moves to the rear and by means of bellcrank I34 the link I38 is moved upwardly. This motion of link I36 is transferred by bellcrank 38 to the link I42 which is moved ahead, and the lever H44 in Fig. 2 is rtated clockwise about the shaft I46. The upper end of lever I44 pulls spring I82 which in turn rotates the bellcrank 14 in the same direction as lever I44 to keep the forward edge of arm I12 against stud 218. Accordingly the input shaft I 4t of the R. P. M. transmitter I48 is rotated clockwise, resulting in a similar rotation of the output shaft 288. Proper rotation of the output shaft I98 also takes place to adjust the potentiometer 232 to result in a higher reading on the simulated tachometer indicator 28?, thus indieating a higher assumed engine speed. The clockwise rotation of bellcrank H4 results in a forward movement of slider I8 3 along link I82, but link i822 does not move because link I82 is normally positioned suihciently far ahead that slider its? does not engage collar I84.

The clockwise rotation of the lever I i-1i will also result in a forward movement or" link 55 It will be appreciated that when the engine speed lever -38 is moved to the rear in Fig. l to produce a lower assumed engine speed, by means of the elements connecting that lever with the lever I44 in Fig. 2, the lever I44 will be rotated counterclockwise. The pin I16 will engage the forward edge of arm H2, resulting in a counterclockwise rotation of the bellcrank I16 and input shaft I46 of the R. P. M. transmitter I48. The output shaft 288 of this transmitter will be rotated counterclockwise through the same angle as the input shaft I 26, and the rotor I98 of the potentiometer 202 will be properly rotated to cause the indicator 281 to indicate a lower assumed engine speed.

The counterclockwise rotation of lever M4 and bellcrank I14 results in a movement to the rear of link I58, and slider E86 slides to the rear along link I82.

Accordingly, the just disclosed apparatus simulates the functioning of the engine being simulated, which engine isequipped with a constant speed propeller, in that the setting of the engine speed control lever I38 normally alone determines the assumed speed of the engine as indicatedby the tachometer 281.

In the functioning of an engine equipped with aconstant speed propeller, the'engine speed is ordinarily determined by the setting of the engine speed lever. However, to maintain any given engine speed for which the engine speed lever may be set, a certain minimum manifold pressure must be produced. Expressed in another manner, for any given manifold pressure there is a highest possible engine speed that may be attainedregardless of the setting of the engine speed lever. The previously disclosed apparatus of this invention simulates this functioning of the engine being simulated in the following manner:

Assuming that the engine speed lever I30 of Fig. l is positioned to produce a certain assumed engine speed, and that the throttle control lever I0 is positioned to produce the required assumed manifold pressure to maintain that assumed engine speed, and the throttle control lever I8 is then moved to the rear to the position which produces an assumed manifold pressure which is less than the manifold pressure required to maintain the speed of the engine at the speed for which lever 53!) is set, the link 88 in Fig. 3 will be moved to the rear resulting in a counterclockwise rotation of the bellcrank I8 and shaft E2. The assembly H2 is energized and the output shaft H9 i rotated clockwise as is the arm I82 carried thereby. The upper edge of this arm engages the pin I94 carried by the arm I86, rotating this arm clockwise and pulling the link I82 to the rear. The movement to the rear of link I82 will result in a similar movement of the collar I84 affixed upon the forward end thereof, and this collar will engage the forward end of slider I which is connected to the arm I12 of bellcrank I14 by means of the pins I11 and I18 and the block I19. Bellcrank I14 will be rotated counterclockwisein the same direction that it is moved when the R. P. M. setting lever I 38 is moved to the rear to produce a lower assumed engine speed. Accordingly, the R. P. M. transmitter I48 will be operated in the required direction to rotate shaft 208 counterclockwise and to rotate the shaft I98 to produce a lower assumed engine speed indication as given by instrument 281.

g The counterclockwise rotation of the bellcrank I14 results in a pulling upon the spring I62, but the lever I44 is not rotated counterclockwise because the link I42 connected to the bottom thereof is held stationary. Consequently, spring I62 becomes elongated.

Generally speaking, arm I92 in Fig. 3 is arranged to engage the stud I94 whenever the assumed manifold pressure is below 36 inches which is the amount necessary to maintain an assumed engine speed of 2800 R. P. M.the highest speed possible of theengine being simulated. As the assumed manifold pressure falls an increasingly greater amount below 36 inches, it will be appreciate'd-that the maximum attainable assumed ongine' speed becomes progressively less. Accordingly, asthe assumed manifold pressure becomes increasingly less, by the arrangement shown in Fig. 3 the link I82 is moved farther to the rear, resulting in a similar movement of the collar I84. This movement to the rear of collar I84 limits the clockwise turning of bellcrank I14 by engaging slide I88, and consequently limits the clockwise positioning of the input shaft I45 of the R. P. M. transmitter I48the direction in which shaft I46 is rotated with an increase in assumed engine speed. Inthe'event the position of collar I84 prevents slider I88'from moving ahead to the position that it would normally occupy for the prevailing position of the engine speed lever I30, the lever I44 assumes its normal clockwise positionfor the setting of the enginespeed lever, but

inasmuch as bellcrank I14 has its clockwise position limited, spring I62 is elongated, and the forward edge of arm I12 merely becomes displaced from pin I16. It will be noted that the position of link I50 is not afiected by the limiting effect of assumed manifold pressure. In the foregoing manner the position of collar I84 which is set by the factor of instant assumed manifold pressure limits the clockwise rotation of the input shaft 146 of the R. P. M. transmitter so that the instant assumed engine speed at no time can be higher than that which can be produced by the instant assumed manifold pressure.

As stated, this arrangement simulates the actual performance of an aircraft engine equipped with a constant speed propeller wherein the actual speed of the engine can be maintained only in the event that sufficient manifold pressure is being produced.

Brake horsepower computer The brake horsepower computer of this invention which combines the factors of instant assumed manifold pressure, instant assumed engine speed and instant assumed altitude to determine the instant assumed brake horsepower being produced will now be disclosed.

Reference is now made to Fig. 4 which is a graph of the actual performance of the engine being simulated by the apparatus of this invention and which shows the brake horsepower produced by the engine under varying conditions of manifold pressure and engine R. P. M. For example, a manifold pressure of 37.5 inches and an engine speed of 2000 R. P. M. produces a brake horsepower of about 1150. Other brake horsepowers for selected manifold pressures and engine speeds may be obtained by inspection from the graph of Fig. 4.

Reference is now made to Fig. 5 where the linkage arrangement of the brake horsepower computer 208 is schematically illustrated, and to Fig. 2 where the actual structure of the computer is shown. The computer includes the fixed pivot which takes the form of shaft 2l0, the output arm of the computer being'designated 2I2 and being affixed upon the shaft 2|0 which is held by bracket I02 by means of set screw 2l4. The pivot 2 l6 pivotally connects the forward end of arm 2l2 with the upper end of link 2l8, the lower end of this link being pivotally held by the master pivot 220 which is free to move in any direction throughout a selected plane. The master pivot 220 also carries the forward end of link 222, the rear end of which is held by pivot 224 which also holds the lower end of arm 226. The upper end of this arm is carried by the fixed pivot which takes the form of a horizontal shaft 223.

The lower end of link 230 is also carried by the master pivot 220, the upper end of this link being attached to the pivot 232 which holds the upper end of link 230 relative to the forward end 234 of the previously mentioned bellcrank 98, the rear end of which is designated 94.

The shaft 200 which is one of the outputs of the R. P. M. transmitter and is always rotationally positioned according to the instant assumed engine speed carries the spur gear 236 which drives the meshing spur gear 238 aflixed upon the left end of the shaft 228. It will therefore be understood that the position of shaft 223 and the position of the arm 226 about the axis of shaft 223 is always in accordance with the instant assumed engine R. P. M,

The apparatus of Figs. 2 and 5 now being considered was designed in the following manner: The location of the fixed pivot 2l0 was selected, the position of arm 2l2 about pivot 2l0 being selected as the measure of the instant assumed brake horsepower. The brake horsepower arc 240 was then drawn, this are having as its center the fixed pivot H0 and being of a radius equal to the length of arm 2|2. The arc was then divided into equal segments of convenient length, to locate a plurality of points therealong, and these points labelled from 200 to 2000 in increments of 200. The length of link 2H8 was then selected, and employing a radius equal to the selected length of link 2l8 a plurality of generally parallel arcs were drawn, each of the arcs having as its center a different one of the prelocated points along are 240. For convenience, each of the arcs so drawn was labelled with the same number or value corresponding to the selected point along arc 240 which is its center.

The position of the fixed pivot 220 was then selected, and a convenient length for the arm 226 was similarly chosen. Using the position of fixed pivot 228 as a center, the R. P. M. are 244 was drawn, this are having a radius equal to the selected length of link 226. Are 244 was then divided into segments of convenient length, to locate a plurality of points therealong, and the points were numbered from 1200 through 2800 in increments of 200. A convenient length for link 222 was selected, and by employing a radius equal to the selected length and using each of the selected points along arc 244 as a center, a plurality of generally parallel arcs 246 were drawn. Each of these arcs may be labelled, for convenience, with the same value as the value of the point along arc 244 used as a center in drawing the arc. It will be noted that the relative positions of the fixed pivots 2 l0 and 228, and the relative lengths of the arms 2 l2 and 226, and the relative length of the links 2I8 and 222, as well as the positions of the arcs 240 and 244 and the length of the segments thereof were chosen so that the brake horsepower lines 242 and R. P. M. arcs 246 run generally at right angles to one another.

The next step was the plotting in of the manifold pressure arcs 250 relative to the constructed brake horsepower arcs 242 and R. P. M. arcs 246 so that for any combination of assumed engine speed and assumed manifold pressure the value of the assumed brake horsepower upon the graphin Fig. 5 would be the same as in Fig. 4 within reasonable tolerances. Perfect conformance between the graphs of Fig. 4 and Fig. 5 is unlikely because of the necessity of producing manifold pressure arcs 250 all having an equal radius, the centers of each of the arcs 250 in turn defining another arc-in this case the are 252. By comparison of Figs. 4 and 5 it will be seen that the given values of manifold pressure and R. P. M. show an approximately equal brake horsepower is produced. For example, in the graph of Fig. 4 a manifold pressure of '34 inches and an engine speed of 2000 R. P. M. produce a brake horsepower of 1000. In Fig. 5 a

manifold pressure of 34 inches and an engine speed of 2000 R. P. M. produce a brake horsepower of 1025.

Having drawn in the manifold pressure are for each value of manifold pressure between 10 and 54 inches, in increments of 2 inches, the center of each are so plotted in was then ascertained. The approximate centers are shown on Fig. 5

asaauac and for convenience are labelled with numbers corresponding to the value of each of the manifold pressure arcs. The approximate center of an are 252 passing through all of the selected centers of the manifold pressure arcs 250 was ascertained, and was selected as the location of the fixed pivot 500, the length of the radius of the are 252 being equal to the length of link 234.

Inasmuch as the shaft 222v is always rotationally positioned by the R. P. M. transmitter [48 in accordance with the instant assumed engine R. P. M., the arm 226 is alwa ositioned about the fixed pivot 228 in accordance with the instant assumed value of the same factor. For example, referring to Fig. 5, when the instant assumed engine speed is 1200 R. P. lVL, 2000 R. P. M., or 25.00 R. P. M., the arm 220 will be positioned so that the pivot 224 is upon the 1200 mark, the 2000 mark, of the 2600 mark, respectively, of are 224. Also, when the pivot 224 is on the 1200 mark upon are 244, the master pivot 220 must be positioned at some point along the 1200 R. P. M. are 246; when the pivot 224 is above the 2000 mark, as shown in Fig. 5, the master pivot 220 must be at some point along the 2000 R. P. M. are 245; and when the master pivot 224 is above the 2600 mark on are 244 the master pivot 220 must be at some point along the 2600 are 242. For any value of instant assumed R. P. M1, the pivot. 224 will be properly positioned along the are 244, and the master pivot 220 will be properly positioned relative to the R. P. M. arcs 246.

By virtue of the apparatus shown in Fig. 3 which is responsive to the positioning of the throttle lever I0, the arm 234 of bellcrank as of Fig. 2 is always positioned about the fixed pivot I in accordance with the instant assumed manifold pressure, and accordingly the pivot 232 will always be positioned along the manifold pressure are 252 of Fig. 5 in accordance with the instant assumed value of that factor. For example, when the instant assumed manifold pressure is inches, the pivot 232 will be above the 10 mark on are 252; when the instant assumed manifold pressure is 32 inches, the pivot 232 will be above the 32 mark on are 252; and when instant assumed manifold pressure equals 50 inches, the pivot 232 will be above the 50 mark on are 252. By virtue of the explained method of construction of the brake horsepower computer 208, when pivot 232 is above the 50 markv ofarc 252, the master pivot 220 must be at some point along the manifold pressure are 25.0 marked 15.; when the pivot 232 is above the 32 inch mark upon are 252, the master pivot 220 must be at some point along the are 250 marked 32,; and when the pivot 232 is above the 34 inch mark along are 252, as shown in Fig. 5, the master pivot 220 will be at some point upon the arc 25.0 marked 34. For any intermediate value of assumed manifold pressure, the position of arm 234 about the fixed pivot I00 will be properly positioned, as will the position of pivot 232 along the arc 252. Accordingly the master pivotv 220 will be properly positioned relative to the manifold pressure arcs 250..

The apparatus shown in the drawings is arranged so that the pivot 224 is positioned along the R. P. M. are 244 according to the indication given by tachometer 207, and so that pivot 252 ispositioned along the manifold pressure are 252 according to the indication given by the manifold pressure, gauge I24. Consequently, the master pivot 220, is properly positioned relative to. the RP; M. arcs 246 in accordance with the instant assumed engine speed, and the master pivot 22!) is properly positioned relative to the manifold pressure arcs 250 in accordance with the instant assumed manifold pressure. Inasmuch as the instant assumed brake horsepower produced by any combination of R. P. M. and manifold pressure may be obtained by reference to Fig. 5, it will be appreciated that by properly positioning the master pivot 220 relative to the manifold pressure arcs 250 in accordance with the instant assumed manifold pressure, as well as positioning the master pivot 220 relative to the R. P. M. arcs 245 in accordance with the instant assumed engine speed, the master pivot 22%) will necessarily be properly positioned relative to the brake horsepower arcs 242 for the instant values of assumed manifold pressure and R. P. M. Accordingly, the pivot 216 will always be positioned along the brake horsepower are 240 in accordance with the instant assumed brake horsepower. For example, in the case illustrated in Fig. 5, when the assumed engine speed is 2000 R. P. M. and the assumed manifold pressure is as inches, the master pivot 220 will be positioned above. the 2000 R. P. M. curve 246 and above the 34 manifold pressure curve 250. This positioning places the master pivot 220 in about the 1025 brake horsepower position, and the pivot 2I6 will be positioned in the 1025 brake horsepower position. If the assumed engine speed were 1400 R. P. M. and the assumed manifold pressure 26 inches, the master pivot 220 would be positioned above the 400 horsepower are 242 and the pivot 216 would be above the 400 mark on are 240.

Inasmuch as the pivot 2H5 is always properly positioned along the are 240 in accordance with the instant assumed brake horsepower being produced, it will be appreciated that the rotational position of the output arm H2 and the rotational position of shaft 2l0 upon which arm 2I2 is fixed may be used as, a measure of the instant assumed brake horsepower.

It will be noted that the graphs of Figs. 4 and 5 show that a negative horsepower is developed under conditions of very low manifold pressure and low engine speed. The engine being simulated does not, of course, ever actually develop a negative horsepower, but in flight when the engine speed and manifold pressure are sufficiently low, the resistance offered by the propeller driven by the engine is greater than the thrust produced by the propeller so that the effect is the same as though a negative horsepower were being produced. By designing the brake horsepower computer so that the master pivot 220 can move beyond the zero horsepower are 246, and so that the output arm 2l2 can move clockwise beyond the zero horsepower position, the net effect of the engine in a plane in actual flight operating at low engine speed and low manifold pressure may be simulated.

In an engine of the type being simulated by the apparatus of this application, an increase in altitude results in an increase in the brake horsepower produced by the engine because of the reduction of back pressure upon the engine. The brake horsepower computer, as thus far de scribed, computes the brake horsepower for an assumed sea level or zero altitude condition. Means will now be disclosed for modifying the assumed brake horsepower produced at sea level by the instant assumed engine speed and manifold pressure as changes in the factor of assumed altitude occur.

Reference is made to Figs. 2 and 1 Where the altitude unit in the trainer is shown in block form and designated 254. The detailed construction of such a unit is immaterial insofar as this application is concerned. The altitude unit may be of the type disclosed in U. S. Patent 2,099,857 dated November 23, 1937 and issued to Edwin A. Link, Jr. for Trainers for Aviators, or of the type disclosed in the copending application of Karl A. Kail Serial Number 672,375 filed May 28, 1946, now Patent Number 2,510,578, issued June 6, 1950, for Aviation Trainer, or of any other selected type. In the illustrated case, the altitude unit 254 positions the flexible cable 256 contained in sheathing in accordance with the instant assumed altitude of the trainer. The worm gears 258 and 26B are similarly positioned, as are the shaft 262 and gears 26-4 and 266, which latter gear is affixed upon the previously mentioned horizontal shaft 64. Shaft 64 carries upon its right end the arm 2&8 which is affixed thereupon by means of set screw 2'59, and the forward end of link 212 is pivotally attached to the upper end of arm 258. The rear end of link 212 is pivotally attached to the upper end of arm 214 and the lower end of this arm is affixed upon the horizontal shaft 2% which is held by the plates 218 and W2, these two plates being fixedly held by the base 219 which is preferably affixed within the fuselage of the trainer. Affixed upon shaft 276 is the gear 286 which is the input gear of the planetary differential desi nated generally by 282. Gear 280 drives the gear 284 which has affixed thereto the gear 286 which drives the spur gear 288 afiixed upon shaft 293 which is held by the differential spider 232. Affixed upon the right end of shaft 2% is the gear 294 which in turn drives gear 295 which is affixed upon the shaft 298 held by spider 292. The gear 298 in turn drives gear 300 which is freely mounted upon shaft 210, but which has affixed thereto the arm 362, to the outer end of which is ailixed the upper end of the vertical link 304. The gears 234 and 286 are freely mounted upon shaft 210, while the differential spider 292 is pinned to shaft 216.

As the shaft 2 I0 is rotated counterclockwise in Fig. 2 as a result of an increase in the sea level brake horsepower, the differential spider 292 will rotate in the same direction carrying the gear 369 therewith. Accordingly, the arm 3G2 which is pinned to gear set will be rotated counterclockwise, and the vertical link 3% will move upwardly. As the factor of assumed altitude in creases, the altitude unit 254 is operated to rotate the gear 266 counterclockwise in Fig. 1, rotating shaft es and arm 268 in the same direction, and moving link 2T2 ahead. Arm 2'52, shaft 216 and gear 28!) are rotated counterclockwise, resulting in a clockwise rotation of gears 284 and 285. Gear 288, shaft 29%, and gear 294 will be rotated counterclockwise, while gear 296 will be rotated clockwise, resulting in a counterclockwise rotation of gear 300 and arm 302, and in an upward motion of link 5184. Accordingly, as the factor of assumed altitude increases, the link 304 is moved upwardly-in the same direction in which it is moved when shaft 2!!) is rotated counterclockwise in. response to an increase in the sea level brake horsepower.

It will be appreciated without a detailedeiiplanation that when the brake horsepower computer output arm N2 of Fig. 2 is rotated clockwise by changes in the instant assumed manifold pressure and R. P. M. to produce a lower assumed brake horsepower, the apparatus shown in Fig. 2 will operate to move the link 364 down-- wardly -in the opposite direction from which it is moved in response to an increase in the factor of assumed brake horsepower. At the same time, when the altitude unit 25 1 is operated to produce a lower assumed altitude, the gear 266 will be rotated clockwise, and through the intermediate connecting elements the gear 300 will be rotated clockwise as will the arm 3G2, and the vertical link this will be moved downwardly.

Accordingly, the planetary differential 282 combines the factor of assumed altitude with the factor of sea level brake horsepower produced, to position the vertical link the in accordance with the instant assumed brake horsepower, and the vertical position of link 364 may be taken as a measure of the instant. assumed brake horsepower, which factor depends upon the controlling variables of assumed engine speed, assumed manifold pressure, and assumed altitude.

The vertical link 3% may be connected to the flight system in the trainer by means of any suitable interconnecting apparatus, as by link 305. The flight system may be of any desired type or construction, and for one such system reference is made to the co-pending application of Charles J. Kidder, Serial No. 778,712, fled October 1947, for Flight Computer for Grounded Aviation Trainers.

In Fig. 2 it will be seen that there is affixed to the arm 302 a pointer 306 which is arranged to move over the stationary dial 388. This dial may be graduated in terms of assumed brake horsepower. By means of this pointer and dial arrangement the instant assumed brake horsepower being produced may be ascertained, and the functioning of the brake horsepower computer 208 may be easily checked by reference to indicator 26'! to determine the instant assumed R. P. M. of the engine, by reference to indicator 124 to determine the instant assumed manifold pressure being produced, by reference to the altimeter in the trainer to ascertain the instant assumed altitude, and then by reference to a suitable graph to ascertain the assumed brake horsepower that should be produced for the prevailing assumed engine R. P. M., manifold pressure and altitude.

Also shown in Fig. 2 is the arm am, the lower end of which is affixed upon the R. P. M. shaft 200 by means of set screw illza. The link 314 has its rear end connected to the upper end of this arm, and this link is connected to the frequency control of the noise system H? to vary the frequency of the noise generated in accordance with the instant assumed R. P. M. of the engine.

M available manifold pressure computers It has been previously explained that in the case of the engine being simulated, which is equipped with a manifold pressure regulator, the setting of the throttle lever normally determines the manifold pressure which will be produced, and the regulator automatically maintains the manifold pressure at that level regardless of changes in altitude and engine speed, unless the combined factors of altitude and engine speed are such that the engine cannot produce the manifold pressure for which the throttle lever is set. It has also been previously shown that the apparatus of this invention provides a simulated manifold pressure gauge connected to the simulated throttle lever so that the reading of the instrument is normally dependent only upon the setting of the lever. In that fashion the functioning of the regulator of the engine in question is simulated, because the reading of the simulated. manifold pressure gauge is normally determined solely by the setting of the throttle lever. To complete the simulation, means will now be disclosed whereby when the factors of assumed altitude and assumed engine speed are such that under corresponding real conditions the regulator in the plane could not maintain the manifold pressure for which the throttle lever is set, the assumed manifold pressure as indicated by the simulated manifold pressure gauge will be limited by the proper amount depending upon the assumed engine speed and altitude.

Inasmuch, as has been stated, the engine being simulated is equipped with a supercharger which may be operated on high blower or low blower, and that for any given conditions of engine speed and altitude the maximum available manifold pressure differs, depending upon whether the supercharger is operating on high blower or low blower, two maximum available manifold pressure computers are provided-one being operative when it is assumed the engine is operating on high blower and the other being operative when it is assumed the engine is Operating on low blower.

Reference is now made to Fig. 1 wherein there are disclosed two novel computing arrangements for limiting the factor of assumed manifold pressure according to the instant assumed values of engine speed and altitude. Two such arrangements are disclosed in Fig. 1, the apparatus designated generally by 3H3 being operative to limit assumed manifold pressure when it is assumed that the supercharger control is in the high blower position, and the apparatus designated generally by 3!!! being operative to limit the factor of assumed manifold pressure when it is assumed that the supercharger control is in the low blower position.

Fig. 6 is a rectilinear graph showing the maximum available manifold pressure produced by an engine of the type being simulated at various altitudes and various engine speeds. For example, this graph shows that at 22,000 feet of altitude and 2000 R. P. M. engine speed, a manifold pressure of inches is produced.

Referring now to Figs. 1 and '7, the previously mentioned horizontal shaft 64 is disclosed, and the lower end of arm 3M is afiixed upon shaft 64 to be positioned thereby. To the upper end of arm 3M the forward end of link 3Ifi is attached by means of pivot 3H3, the rear end of this link carrying the pivot 320 to which is pivoted the upper end of link 322. The pivot 324 connects the lower end of link 322 and. the rear end of arm. 325, the forward end of arm 32% being freely mounted upon shaft 64. The upper end of link 328 is also pivotally carried by pivot 320, the lower end of this link being held by pivot 33!! carried by the rear end of arm 332 which, together with the arm 334, forms a bellcrank 335 which is pivoted upon the fixed stud 33 which is held by the casting 65. The elbow of the bellcrank 335 carries the pivot 338 upon which is mounted the forward end of link 340, the rear end of this link being carried by pivot 342 which in turn is held by arm I56 which, as previously described. has its lower end mounted upon the fixed pivot I58. It will be recalled that the extension I5 of arm I56 is pivotally connected to the link I 50 which moves ahead in response to an increase in assumed engine speed, and to the rear in response to a decrease in assumed engine speed.

In Fig. 1 it will be seen that an insulating disc i l-l is provided, this disc being coaxial with the shaft $6 and fixedly attached to arm 32% to be rotationally positioned thereby. A pair of mutually insulated contact segments 3% and 348 are affixed to the insulating disc 3% to rotate therewith. A spring contact 350 is attached to the gear 352 by means of rivets 35 to be rotationally positioned thereby, this spring contact being arranged to engage at all times one or both of the split contact segments 346, 3 38, depending upon the relative rotational positions of the contact 353 and split contact segments. The gear meshes with the splined rod 3% to be driven thereby, this splined rod in turn being the output shaft of the reversible follow-up motor 358. A second gear 350 meshes with the splined shaft 356 to be driven thereby, both of the gears 352 and 338 being freely mounted upon shaft 66. The gear 330 carries the pin 362 which is displaced from the axis of shaft 64 an amount equal to the displacement of the boss 364 which is integral with the left side of lever '52. Pin is sufficiently long to engage the boss 364 to rotate the lever 62 counterclockwise under conditions to be described.

Reference is now made to Fig. 7 which schematically discloses the computing arrangement of the apparatus for limiting manifold pressure when the supercharger control is in the high blower position, as well as the graphical basis for said computing arrangement. The axis of shaft t l determines the fixed pivot of the link Gi l, and the altitude arc 482 is drawn with its center at the axis of shaft 64 and on a radius equal to the length of arm SW. The altitude arc M32 is then marked off into convenient equal increments of length, and using a radius equal to the selected length of link 3I6, a plurality of altitude arcs 404 were drawn from the various points upon are 462 previously marked off. The various points upon are 402 are labelled in convenient numbers designating thousands of feet of altitude, and each of the arcs 404 is designated with the value of the number along are 402 serving as its center.

Again using the axis of shaft 64 as a center, the are 405 was described, the radius of this arc being equal to the length of link 326, the length of which equals, in the selected case but not necessarily, the length of link 3M. Arc 4'95 was then marked on in equal increments, and each of the points upon the are given a value from 10 to in increments of 5 inches of manifold pressure. From each of the points upon are 108 a manifold pressure are 408 was described, and each of these arcs labelled with the same number as the point along are 4% serving as its center. The engine speed curves 4H!) were then drawn in relative to the previously described curves 404 and 408 so that for any combination of assumed altitude and assumed engine speed the value of the manifold pressure upon the graph in Fig. '7 would be the same as in 6 within reasonable tolerances. Perfect conformance between the graphs of Figs. 6 and 7 is unlikely because of the necessity of producing the engine curves All!) in the form of true arcs of the same radius, the centers of each of the arcs in turn being in the form of a true arc, as will become more apparent later.

The are M5 was then drawn with its center at the point I58 and using a radius equal to the distance between pivots I58 and 342. Arc M was then divided into equal parts, and the division marks labelled with the proper values of assumed engine speed. The interconnecting mechanism between the engine speed lever I36 and the arm 155 is arranged so that when lever 130 is in the 1200 R. P. M. position, 1400 R. P. M. position, etc., the pivot S42 is upon the 1200, 1400, etc. mark on are H5. When the pivot 342 is on the 1200, 1400, etc. mark on are M5 it is necessary that the master pivot 320 be above the correspondingly numbered engine speed curve M0. To accomplish this result, it is necessary to provide suitable mechanism interconnecting the pivot 302 and the master pivot 320 which will convert the linear movement along arc M5 for equal changes in assumed en ine speed into the required non-linear movements between the engine speed arcs M0 for equal changes in assumed engine speed. This interconnecting mechanism takes the form of the link 340, bell crank and link 32%, together with their associated pivots. This portion of the apparatus was designed as follows:

As previously explained, the engine speed curves M0 are arcs of the same radius, this radius being equal to the length of link 328, and the center of each of these arcs in turn define the arc M2 which has its center at the pivot 335. Each of the centers of the arcs 4 i 0 is marked on are M2 and correspondingly numbered. The points thereon, as shown, are non-linearly spaced. By providing bell crank arm 334 pivoted at 330 and its arm 332 connected to link 320 at pivot 330, and by interconnecting arm I55 with link 340, the linear motion of arm I56 which takes place with changes in assumed engine speed is converted into the proper non-linear metion of pivot 330 along arc M2 and of the master pivot 320 relative to the engine speed curves liii.

Accordingly, when the pivot 342 is upon the 1200, 1400, etc. R. P. M. mark on are M5, pivot 338 will be above the corresponding valued points of arc 4M and pivot 33!! will be above the correspondingly valued points along arc 412. Ac-

cordingly, the position of pivot 320 relative to the engine speed curves M0 will be according to the position of pivot 342 along arc M5, the position of which depends upon the setting of the engine speed lever I30.

The positions of the parts of the maximum available manifold pressure computer for the high blower supercharger condition when the engine speed lever N20 is in the 2000 R. P. M. position are shown in Fig. 7.

It will be recalled that the gear 200 in Fig. 1 is always rotationally positioned in accordance with the instant assumed altitude, this gear being rotated counterclockwise with an increase in assumed altitude. Inasmuch as this gear is pinned to the shaft 64, the shaft 84 is always rotationally positioned in accordance with the instant assumed altitude. Arm 31G is affixed to shaft 64 to rotate therewith, and consequently this arm will also always be positioned in accordance with the factor of instant assumed altitude. Accordingly, the link 3 I B which interconnects the upper end of arm 314 with the master pivot 320 will always position the master pivot 320 relative to the altitude curves 404 in accordance with the instant assumed altitude.

In the case shown in Fig. 7, when assumed altitude is 20,000 feet, the arm 3M, pivot 3l8, link M6 and pivot 320 will be positioned as shown.

Consequently, the master pivot 320 is always positioned relative to the engine speed curves 4 1'0 and the altitude curves 404 in accordance with the instant assumed engine speed and altitude. Accordingly, the master pivot 320 will at all times be properly positioned relative to the manifold pressure curves 003 for the existing assumed engine speed and altitude, and by means of link 322 which interconnects the master pivot 320 with the arm 32:3, the arm 328 will always be positioned about the axis of shaft 64 in a position corresponding to the maximum available manifold pressure for the existing assumed altitude and engine speed. The position of the split contact segments 5% and 3 18 is changed by any change in the position of the maximum manifold pressure available arm 32S, and for present purposes it is merely stated that the motor 3523 always functions as a result of any rotation of the contact segments to rotate the splined shaft 350 and gear 352 through the same angle and in the same direction as the rotation of the contact segments to bring the contact 350 to the same rotational position as the contact segments 346 and 348, at which instant motor 358 stops. While motor 358 is so returning the contact leaf 350, gear 300 is rotated in the same direction and through the same angle as the contact segments. Accordingly, the pin 352 carried by gear 360 is at all time positioned in accordance with the position of the maximum available manifold pressure arm 326, the position of which is a measure of the instant assumed maximum available manifold pressure. The electrical circuit interconnecting the contact segments 305, 3 38 and motor 350 will be hereinafter disclosed.

The rotational position of lever 62 in Fig. 1 cannot at any time be farther clockwise than the position of pin 362 because of the engagement of boss 304 by pin 302. If the student in the trainer pushes the throttle lever IE! sufficiently far ahead to normally produce a higher instant assumed manifold pressure than it would be possible for the engine being simulated to produce with the existing R. P. M. setting and altitude, the stop 365 on lever 62 will engage the pin 30?, and further clockwise rotation of the lever 62 will be prevented. The collar 58 pressing against the compression spring will compress the spring, but the link 68 attached to the bottom of lever 62 will not move ahead once the stop 364'. has engaged pin 362. although the link 08 normally is moved ahead in response to a forward movement of the throttle lever l0the position of this link being a measure of the instant assumed manifold pressure, which factor is primarily determined by the throttle lever settingwhen the instant assumed altitude and engine speed are such that the engine cannot produce the manifold pressure for which the throttle lever is set, the maximum available manifold pressure computer 1H0 limits the forward movement of link 68, thereby limiting the instant assumed manifold pressure. Consequently, the indication given by the manifold pressure indicator I24 in Fig. 3 will not exceed the instant available maximum manifold pressure, and the manifold pressure input to the brake horsepower computer in Fig. 2 Will not exceed the same factor.

Also, in the instance where during the operation of the apparatus of this invention the factors of assumed altitude and engine speed are such that the manifold pressure for which the Accordingly,

throttle lever is set may be developed when the supercharger is in the high blower position, and subsequently the assumed engine speed is decreased and/or assumed altitude is decreased beyond the limits within which the engine being simulated could maintain the manifold pressure for which the throttle lever is set, the maximum available manifold pressure computer 3H) will at the proper time and to the proper extent operate the motor 358 to rotate gear 36% counterclockwise so that p-in 342 engages stop 364 to rotate lever 62 counterclockwise and move link 68 to the rear by the proper amount.

Consequently, by the provision of the computer disclosed in Fig. 1 and described above, the functioning of an engine of the type being simulated wherein the instant available manifold pressure is primarily determined by the setting of the throttle lever but is limited by the prevailing engine speed and altitude is accurately simulated, for the case when the supercharger of the engine is in the high blower position.

An arrangement quite similar to that disclosed in connection with the assumed high blower supercharger position is also provided for simulating the limiting effect of engine speed and altitude when the supercharger is assumed to be in the low blower position. Such means will now be described.

Reference is now made to Fig. 8 which is a rectilinear graph showing the maximum available manifold pressure for various conditions of altitude and engine speed of the engine being simulated when the supercharger is in the low blower position, and to Fig. 9 which is a curvilinear graph based on the graph of Fig. 8. The graphs in Figs. 8 and 9 show somewhat different values for the maximum available manifold pressure from the values shown in Figs. 6 and '7 for corresponding values of altitude and engine speed, the differences being attributable to the supercharger effects upon the manifold pressure produced. For example, in Fig. 6, which shows engine performance when the supercharger is in the high blower position, when altitude is 22,660 feet and the engine speed is 2000 R. P.

the manifoid pressure produced is 25 inches, while in Fig. 8, which shows, engine performance when the supercharger is in the low blower position, when assumed altitude is 22,000 feet and engine speed 2000 R. P. 1\/i., the manifold pressure is approximately 19 inches. In both Figs. '7 and 9 it will be seen that the assumed altitude, in the cases illustrated, is 20,000 feet, and that the assumed engine speed is 2005) R. P. M. In Fig. 7, which illustrates the case when the supercharger is assumed to be in the high blower position, the assumed manifold pressure is about 2'7 inches. However, in Fig. 9 which illustrates the case where the supercharger is in the low blower position, the assumed manifold pressure produced is about 20.5 inches.

Inasmuch as for any combination of altitude and engine speed in the case of the engine being simulated, the maximum available manifold pressure varies depending upon whether the supercharger is in the high blower or low blower position, it becomes clear that in order to accurately simulate the performance of the engine in question it is necessary to provide a pair of computing arrangements to limit motion of link 68 in Fig. 1 depending upon whether the student has the simulated supercharger control in the high blower or low blower position.

Referring now to Figs. 1 and 9, it will be seen that the maximum available manifold pressure computer for the low blower condition is designated generally by M2 and includes the arm 420 afiixed upon shaft 64 to rotate therewith. The forward end of link 422 is pivotally connected to the upper end of arm 420 by pivot 422i, and the rear end of this link is carried by the master pivot 424. The upper end of link 426 is also carried by pivot 424, the lower end of this link being connected to the outer end of arm 428 by pivot 430. The forward end of arm 428 is freely mounted upon shaft 84. The upper end of arm I56 is carried by pivot 432, as is the upper end of link 434, the lower end of which is carried by pivot 436. Pivot 435 connects the lower end of arm 434 with the lower end of arm 4538, the upper end of which is held by the fixed pivot 440 which takes the form of a stud rotatably held in the boss 442 which is affixed to the casting 55. Lastly, the link 444 is provided, this link having its lower end carried by pivot 446 which in turn is carried by arm 43-8, the upper end of link 444 being carried by the master pivot 424.

Referring to Fig. 10, it will be seen that the insulating disc 50% is affixed to arm 428 by means of rivets 542, and that this insulating disc carries the two mutually insulated contact segments 534 and 588. A spring contact 588 is pinned to gear 5H! by rivets El2, gear m being freely mounted on shaft 64 and meshed with splined rod 356 of Fig. 1 to be driven thereby. The contact arrangement just described is esentially the same as that previously disclosed in connection with the high blower maximum available manifold pressure computer 31!).

Referring now to Fig. 9, the basic altitude are 454 is divided into convenient increments of altitude, and the altitude curves 452 are drawn therefrom in the same manner as described in connection with Fig. I, employing a radius equal to the length of link 422. Also the basic manifold pressure are 454 is divided into convenient increments of manifold pressure, and the manifold pressure curves 456 are drawn therefrom in the manner previously described, employing a radius equal to the length of link 426. The R. P. M. curves 458 are plotted in from the information shown in Fig. 8, as previously described, and the center of each of these curves is plotted and numbered, and the arc 450 drawn therethrough, the center of this are being the fixed pivot 44! The lower end of link 444 is attached to arm 438 at a distance from the fixed pivot 440 equal to the radius of the are 46% by pivot 46L the length of link 444 being equal to the radius of the engine speed curves 458. The are 454 is drawn, using a radius equal to the distance from pivot I58 to the pivot 432, and this are is divided into increments of equal length for equal changes in the factor of assumed engine speed. In order to convert the linear movement of pivot 432 along are 464 with equal changes in assumed engine speed into the required non-linear movement of arm 438 along are 458 and of master pivot 424 relative to the non-linearly spaced engine speed curves 458, the link 438 is extended beyond pivot 46!, and the lower end of this link used to describe the are 462 concentric with are 464. Arc 462 is divided into non-linear increments labelled with values corresponding to those on are 464 for given positions of the radius link 4153. The link 434 connects the pivot and pivot 436 at the outer end of link 433 to convert the linear motion of pivot 432 into a non-linear motion of pivot 43% 21 along are 552, of pivot 56% along are 468, and of the master pivot 424 relative to the engine speed curves 458.

The electrical circuit interconnecting contact segments 564, 558 and motor 358 will be hereinafter disclosed.

In View of the preceding disclosure of the available manifold pressure computer disclosed in Figs. 1 and 9, it will be appreciated that the arm N55 is always positioned about the fixed pivot Hit in accordance with the instant assumed engine speed, and by means of link 454 the arm is always correctly positioned about pivot 555 and along are 455 in accordance with the same factor. By means of link M4 the master pivot did is always properly positioned relative to the engine speed curves 58 for the instant assumed engine speed.

Inasmuch as shaft is always rotationally positioned in accordance with the instant assumed altitude, the arm 22 will be similarly positioned, and by means of link 4222 the master pivot 424 is always properly positioned relative to the altitude curves 552 in accordance with the factor of instant assumed altitude. Accordingly, by means of link 428, the pivot 335 is always positioned along arm .5 and the arm 525 is always properly positioned about the of shaft 55 in accordance with the instant assumed maximum available manifold pressure for the prevailing assumed altitude and engine speed. The split contact segments will alwa s be positioned in accordance with the instant assumed inaidmum available manifold pressure any displacement of the contact 558 from engagement with both the split contact segments 5% and 558 will energize motor 358 to drive the splined shaft 355 and gear 5 I 8 to bring the contact 558 back into engagement with both of the split contact segments, at which instant the motor will stop. At the same time the rotation 01 the splined shaft 555 will position the gear 355 and pin 352 which controls the clockwise rotation of lever 52. Consequently, by means of the disclosed follow-up system, the gear 359 and pin 362 are positioned in accordance with the position of arm 42%, which arm is positioned according to the maximum available manifold pressure for the low blower supercharger condition. Accordingly, when the supercharger control is in the low blower position, if the throttle lever it is positioned ahead to produce an assumed manifold pressure greater than the maximum available manifold pressure for the assumed altitude and engine speed, the computer 3i? by positioning pin 352 prevents the link 68 from being positioned farther ahead than the position which it should occupy for the value of the instant assumed maximum manifold pressure available. Consequently, a proper assumed manifold pressure is indicated by the manifold pressure indicator E25 in Fig. 3 and is introduced into the brake horsepower computer of Fig. 2.

Reference is now made to Fig. 11 which discloses the electrical system which is associated with the maximum available manifold pressure computing apparatus disclosed in Fig. l. in 11 the contact segments 554, 555 and the spring contact 558 associated with the low blower maxi mum available manifold pressure computer 5|? are shown. Spring contact 558 will be seen to be grounded. The spring contact 525 is arranged to bear against the periphery of segment 5%, and this contact is connected through conductor 522 to the contact point 524. When the movable contact 526 is in engagement with contact 52 3,

the contact 524 is conected by conductor 528 to contact 535. When the movable contact 532 is in engagement with contact 5%, contact 535 is connected through conductor 535 with the lower shading coil 555 of the previously mentioned shaded pole reversible follow-up motor 358. The contact segment 556 is engaged at all times by the contact member 538 which is connected through conductor 546 with the contact 542, and when the movable contact 54 is engaged with the contact 542, contact 542 is connected through conductor 546 with the fixed contact 548. When the movable contact 55?; engages the fixed contact 5 35, contact 553 is connected through conductor 555 with the upper shading coil 555 of motor 353. The lower end of shading coil 555 and the upper end of shading coil 536 are grounded through conductor 558 and the conventional adjustable resistor 559.

The contact segments 346, 358 and contact 355 which are associated with the high blower maximum available manifold pressure computer 3H5 are also shown in Fig. 11. Contact its will be seen to be grounded. The contact 552 is arranged to engage the segment 346 at all times, and 552 is connected through conductor 564 with the fixed contact and when the movable contact 525 engages fixed contact 585, fixed contact 566 is connected through conductor 528 with the fixed contact 555. As previously stated, when the movable contact 552 engages fixed contact 5311, contact 536 is connected through conductor 534 with the lower shading coil 535. The contact 5'55 is arranged to engage the contact segment at all times, and contact 510 is connected through conductor 512 with the fixed contact 5%. When the movable contact 544 engages the fixed contact 51 8, contact 574 is connected through conductor 545 with the fixed contact 558. When the movable contact 555 engages the fixed contact 548, as previously explained, fixed contact 5 28 is connectedthrough conductor 555 to the upper shading coil 556.

The field coil of motor 358 is designated and it will be seen that by means of conductors 5'l8 and 555 a volt potential is impressed across this field coil at all times. In Fig. 11 it will also be seen that the conductor 582 connects to one side of the 110 volt potential, and that this conductor is in the circuit including the supercharger control 584 which is schematically shown in Fig. 11 as being a switch. This switch, which is manually operated by the student receiving instruction by the use of the trainer of which the apparatus of this invention forms a part, connects the conductor 582 with the conductor 586 and relay 588. Relay 588 is connected, on its other side, by the conductors 595 and 518 with the other side of the 110 volt line.

The master relay 592 is energized whenever it is assumed that the engine in the trainer is running, as disclosed in the previously mentioned patent application Serial Number 634,492, now Patent Number 2,510,500, issued June 6, 1950, so that the'movable contact 594 is normally disengaged from the fixed contact 596, opening the circuit including ground, conductor 558, contacts 595 and 555, conductor 855, the power failure relay E52, conductor 554 and conductor 532 which connects with the hot side of the 110 volt source. Accordingly, the power failure relay 502 is normally de-energized.

Assuming that the supercharger control 584 is in the high blower position, in which position switch 585 is closed, the relay 588 will be energized, resulting in an engagement between the movable contact 544 and the fixed contact 514, and in an engagement between the movable contact 526 and fixed contact 566. No engagement will be made between the two pairs of contacts 544 and 524, 526. The power failure relay 602, being normally de-energized will permit engagement between the contacts 548 and 555, as well as between the contacts 530 and 532. Accordingly, the contact 562 which engages the contact segment 346 will be connected through the electrical elements 565, 566, 523, 528, 536, 532, and 535 with the lower shading coil 536, and the contact 5% which engages the contact segment 34-6 will be connected through electrical element 5'52, 574,5 i#.,5 i6,568,556, and 554 with the upper shading coil 555.

When the grounded contact 356 engages both of the contact segments 346 and 348, through the just described electrical connections both coils and of motor 353 will be grounded at both of their ends, and consequently motor 358 will not run. However, whenever the factor of maximum available manifold pressure as computed by the computer EH6 of Fig. 1 is decreased, as previously explained the arm 326 will be rotated counterclockwise resulting in a similar rotation of the contact segments 346 and 343. Consequently, the contact 358 will be momentarily disengaged from the contact segment 346, and the lower shading coil 536 will no longer be grounded at both ends. Motor 353 will immediately be energized to rotate the output shaft 356 in the clockwise direction, resulting in a counterclockwise rotation of the gear 352 until the contact 358 is rotated through the same angle as the contact segments 346 and 3% were rotated in response to the decrease in assumed maximum available manifold pressure. When this rotation has taken place, the contact 356 will again engage both or" the contact segments 346 and 348, at which instant both of the shading coils 536 and 556 will be grounded, and motor 358 will stop. At the same time that gear 52 is being rotated counterclockwise by the splined shaft 356, the gear 355 is similarly rotated, carrying pin 352 counterclockwise through the same an le as the contact 35!], thereby limiting the clockwise rotation of lever 62 and the forward movement of the link 56, the position of this last link being the measure of the instant assumed manifold pressure.

011 the other hand, whenever the maximum available manifold pressure computer 3 l of Fig. l is operated to rotate the arm 326 clockwise in response to an increase in the maximum available manifold pressure, the contact segment 35!! will become disengaged from the contact segment 348, and the upper shading coil 556 of motor 358 will no longer be grounded. Accordingly, motor 358 will be instantly energized to rotate in the Opposite direction from that just described, resulting a counterclockwise rotation of the output shaft 556 and in a clockwise rotation of the gear 352. The e movements will continue until the gear 352 and contact 356 have been rotated through the same angle as the contact segments M6 and 3 58 were rotated in response to the increase in assumed maximum available manifold pressure, at which time the contact 353 will again engage both of the contact segments 346 and 34B and motor 353 will stop. The clockwise rotation of gear 352 is accompanied by a similar rotation of gear and pin 362, permitting a greater clockwise rotation of lever 62 and a further movement ahead of the link 66. Consequently, a

24 greater assumed manifold pressure may be obtained.

When the supercharger control 58 1 is positioned by the student in the low blower position, the switch 584 is open and the relay 588 is de-energized. Consequently, no contact will be. made between the contacts 5M and. 5'54, nor between the contacts 566 and 526. Such being the case, the contact segments 3 36 and 348 together with the contact 353 are no longer operable to regulate the operation of the follow-up motor 353, but by virtue of the fact that the contacts 542 and 544, on the one hand, and the contacts 524 and 526, on the other hand, will then be engaged, it will be appreciated that the contacts 526 and 538 which bear against the contact segments 564 and 565 are connected to the shading coils 536 and 556. Accordingly, when the movable contact 508 engages both of the contact segments 504 and 566, both of the shading coils 536 and 556 will be grounded, and motor 358 will be de-energized. When the low blower maximum available manifold pressure computer 352 is operated to rotate the contact segments 56 i and 596 in one direction or another, depending upon whether the assumed maximum available manifold pressure is increased or decreased, the follow-up motor 358 will be energized to rotate the splined shaft 356 in the proper direction, to rotate the gear 516 and contact 508 in the same direction and through the same angle as the contact segments 504 and are rotated, to bring the contact 568 back into engagement with both of the contact segments 564 and 5% to de-energize motor 558. The rotation of splined shaft 356 of course properly positions the gear 386 and pin 352 to limit the position of link 66, as previously explained.

Accordingly, the position of the supercharger control 584 determines which set of contact segments controls the operation of motor 358, thereby regulating the position of pin 362 according to whether the engine is assumed to be operating upon high blower or low blower. As previously explained, the maximum available manifold pressure of the engine being simulated for identical altitudes and engine speeds is difierent when the engine is operating in the high blower and low blower conditions.

The engine being simulated cannot produce a manifold pressure higher than 49.5 inches when it is operating upon the high blower, nor can it produc a manifold pressure greater than inches when operating in the low blower condition. The following apparatus limits the assumed manifold pressure according to whether the supercharger control 534 is in the high blower or low blower condition.

Reference is made to Fig. 12 which shows the gear 369, also seen in Fig. 1, and the pin 382 carried thereby. Aflixed to the left side of the gear to be carried thereby is the contact 696 which is arranged to engage the roller 692 of micro-switch fla l to close the same when gear 366 is rotated into the 19.5 inch assumed manifold pressure position.

Referring to Fig. 11, the switch 654 is shown .onnected by conductor 356 to the conductor 2 which connects with the upper coil of the motor 358 when the supercharger control is in the high blower position. The other side of switch is groundec. Accordingly, when the supercharger contro 534 is in the high blower position and assumed manifold pressure reaches 49.5 inches, switch 594 is closed, and both sides of coil 555 are grounded. At the same 

